Springerville Generating Station Unit 4 is one of two new coal plants at the site, which already had two other existing 380 MW units. Tucson Electric Power Company (TEP) operates the unit and output is divided among TEP (100 MW), Salt River Project (100 MW) and Tri-State Generation and Transmission Association (218 MW).[1] Coal is supplied by the North Antelope Rochelle Mine, south of Gillete, Wyoming.[2]

Springerville Units 3 and 4 were the subject of a lawsuit brought by Arizona Center for Law in the Public Interest on behalf of Western Resource Advocates and Grand Canyon Trust. After a series of court decisions and hearing, a settlement was reached that allowed construction of the plants in exchange for lowered emissions and investment in renewable energy and energy efficiency programs.[3] Unit 4 is projected to be complete by December 2009.[4]

On May 6, 2008, the Sierra Club sent a maximum achievable control technology (MACT) notice letter to Tucson Electric requiring the company to install technology to control mercury and other hazardous air pollutant emissions from the proposed units. By July 2008, Springerville Generating Station Unit 3 was operational.[5]

On December 31, 2008, Unit 4 suffered a fire estimated to have caused $10 to $12 million in damage. While some construction has been rescheduled, the plant is projected to begin commercial production by the end of the year. It will begin burning oil in September 2009 and switch to burning coal soon after.[6]

On March 18, 2010, the Arizona Department of Environmental Quality issued a revised, draft Title V operating permit for Tucson Electric Power's Springerville Station, which incorporates mercury emission limits for the project. Unit 4 began operating in December 2009.[5]

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Energy Production and Consumer Costs

Springerville Generating Station's Unit 4 burns approximately 60 rail cars' worth of coal daily. The coal is mined in the Powder River Basin of Wyoming. In the spring of 2009, customers will begin paying about $6 more on their monthly bills. The costs are due to the fact that the plant's construction overshot its cost by $350 million. Pending climate legislation could also make the plant's operations more expensive if it is forced to install pollution reduction equipment. As a result, popular support for the plant has waned.[7]